This research project is concerned with defining possible abnormalities in the lipid and apoprotein composition of the plasma lipoproteins in subjects with diabetes mellitus and to investigate certain aspects of lipoprotein catabolism with specific reference to the activity of various lipoprotein lipases and lecithin: cholesterol acyltransferase. The object of these studies is to possbibly define specific abnormalities in lipoprotein composition or metabolism which might be considered unique to this disease and therefore represent abnormalities which could account for the significant increased incidence of vascular disease in patients with diabetes. To investigate the dyslipoproteinemia of diabetes complete lipid and apoprotein compositional studies of all classes of plasma lipoproteins will be determined in subjects with controlled or uncontrolled diabetes and in subjects with diabetic ketoacidosis. In addition to compositional studies the levels of hepatic and extra-hepatic triglyceride lipases and lecithin; cholesterol acyltransferase will be determined. The effects of insulin on the dyslipoproteinemia will be investigated by performing sequential studies in subjects with marked hyperlipidemia who will be treated with insulin according to precise regimens. This data should help to elucidate possible defects in lipoprotein metabolism in diabetes and may provide information regarding specific biosynthetic or catabolic abnormalities which may be restricted to the diabetic state.